DESCRIPTION: (Adapted from applicant's description) This proposal focuses on culture conditions that allow the oocyte to achieve full competence for fertilization and development. This competence is acquired during oocyte growth and development and is established by the environment of oocyte development and genetic programs intrinsic to the oocyte. The investigators have devised serum-free culture systems in which oocytes, even those from primordial follicles, grow and acquire competence to undergo embryogenesis. However, the growth and development of the oocytes is not the equivalent of oocytes grown in vivo. It is hypothesized that improvement of the development of oocytes in vitro is dependent upon (1) suppressing apoptosis in granulosa cells and (2) promoting the appropriate differentiation of the granulosa cells coupled to the oocytes. This will be tested in the first two specific aims. In Specific Aim 1, will determine whether suppressing apoptosis in long term culture of oocyte-granulosa cell complexes initially prepared from preantral follicles will (1) sustain communication between the granulosa cells and oocytes, (2) increase oocyte growth and the rate of germinal vesicle breakdown (GVB), (3) improve the competence of the oocytes to undergo fertilization and embryogenesis, and (4) promote a pattern of gene expression in the cultured oocytes that is similar to that of oocytes grown in vivo. Specific Aim 2, will determine whether (A) suppressing the follicle-stimulating hormone (FSH)-stimulated expression of the characteristics of mural granulosa cells and (B) promoting the development of the characteristics of cumulus cells in the oocyte-associate granulosa in long term cultures of oocyte-granulosa cell complexes initially prepared from preantral follicles will (1) increase oocyte size and rate of GVB, (2) improve the competence of the oocytes to undergo fertilization and embryogenesis, and (3) promote a pattern of gene expression in the cultured oocytes that is similar to that of oocytes grown in vivo. Aim 3, will identify genes transcribed during oocyte development that are essential for the development of embryos from the 2 stage to blastocysts by comparing transcripts in these oocytes with those of normal, developmentally competent oocytes grown in vivo.